In American Cardiovascular Journal (32 (10) 656-661, 1973) Dr. Cohen has reported a device for external counterpulsation, a four-limb sequential counterpulsation device. It consists of multiple balloons wrapped around the four limbs of the patient. The pressure is applied sequentially from the distal portion to the proximal portion of the four limbs. Using high pressure gas for its source of energy (1000 to 1750 mm Hg) and by controlling the time of opening of the solenoid valve, the balloons receive a fixed amount of air during inflation; and by using a vacuum pump the balloons deflate. The necessity of using a large air compressor vacuum pump set and pressure monitoring device is to insure that no excessive pressure is exerted in the balloons. However, the device is bulky, causes loud noises is complicated to operate, and expensive. It is, therefore, unsuitable for clinical use.
The inventor of the above mentioned device, however has introduced and adopted another device of sequential counterpulsation on the four limbs without the source energy from high-pressure gas and the vacuum pump. The device makes use of a low-pressure large-flow pump to supply oil-free gas. In this way the size of the apparatus is decreased and the noise is reduced to below 62 db. Owing to the adoption of a larger channel and fixed time of inflation (100 m sec.) and keeping the pressure in the gas reservoir at 270 to 300 mm Hg, the pressure in the balloons is constant. There is no need to install a pressure monitoring system, and so the operation is relatively simple. The diastolic pressure is augmented by 32%. Ear-pulse waves have shown that the ratio of diastolic wave amplitude to that of systolic wave amplitude (D/S) is equal to 1.32.+-.0.19. The clinical and experimental data have shown that in order to get better counterpulsation effect and to promote the establishment of collateral circulation it is necessary to raise the diastolic pressure to a certain level.
In that device of counterpulsation the augmentation of diastolic pressure is not conspicuous enough. Besides, the ECG analogue filter, the R wave detector and the R--R integrator of the inflation-deflation processing device are all of the analogue circuit. Therefore, the control of inflation-deflation timing is less accurate and their range is small. The device has no automatic delay control function, is large and bulky, and emits excessive noises. The bed for counter-pulsation is flat and therefore uncomfortable for the patient. The clinical results are not satisfactory.
Besides, the extrathoracic cardiac massage apparatus in current use is one that is placed at the lower portion of the sternum. The massage head is periodically lowered down and presses over the sternum so that pressure is exerted over the heart and the great vessel underneath, thus drives the blood to the periphery to achieve resuscitation. Yet, this method cannot expel an adequate amount of blood from the heart and the big vessels in the left chest. The amount of blood expelled is limited and cannot meet the physiological requirements. When the chest receives pressure the venous blood is expelled from the chest cavity. Due to the relaxation of the peripheral vessels, a great amount of blood is stored in the blood vessels, which in turn causes brain anoxia. Besides, the brain anoxia and the relaxation of the peripheral vessels, a great amount of blood is stored in the blood vessels so that the return of venous blood to the heart is decreased, central venous pressure is low, cardiac output diminishes, the arterial perfusion to the brain is low and is even lower to the cardiac muscles. Through years of clinical practice this method has proved that it offers less chance of resuscitation.